Well, can you make a new sitemap and see if the weird links (with digits) appear in that? I made your sitemap at xml-sitemaps.com and the 500 links (limit in their free service) does not contain any such weird links. It is an indication that they are actually not there.

Thanks for the examples, everyone! It does look like we’re picking up something funny via JavaScript there. We’re looking into what can be done in this particular case. In the meantime, keep in mind that 404 errors of URLs that are invalid (like these appear to be) are not something that would affect your site’s indexing or ranking, so while I understand that they may be confusing (and I’m sorry for the number of URLs here), it’s not something that you’d need to take action on.

Thanks krishna for searching on google forum. I was aware of this fact because matts have told this fact many times in his videos that 404 error stays fro some time in GWT and than google remove it over a period of time.
The reason of showing 404 error is that google want to inform you that some of your website pages are not working so please make them available for others. it may be the reason some one made changes on server which causes this error for fews pages google don’t want to remove those pages instantly from google search results so it keep those pages(404) for certain time.
This is not known.